(a) Field of the Invention
The present invention relates to a geartrain, and more specially, to a geartrain for a five forward speeds and one reverse speed automatic transmission, which can be designed to be lightweight and compact in size by combining a clutch, brake, and planetary gearset efficiently.
(b) Description of the Related Art
Generally, an automatic transmission system controls each element of single planetary gearsets which are connected to either operative or inoperative friction elements by a hydraulic control system of a transmission control unit (TCU), so that the automatic transmission system automatically controls shift ratios.
A geartrain is typically described with a combination of planetary gearsets and friction elements to realize shift ratios.
The above described geartrain is variously composed according to shift ratios and the geartrain is composed of primary and sub shifts combining seven clutches and brakes and three single planetary gearsets especially for realizing five forward speeds and one reverse speed.
However, the above described geartrain for an automatic transmission becomes large in size and heavy because of the use of heavy and large-size clutches and brakes and a plurality of inoperative friction elements, which results in power loss.